Fish store water 48 ppt / 1.035

[mike31154]

Never a bad idea to have a second hydrometer kicking around, even a cheap swingarm one. You can put a mark on them based on an accurate refractometer reading & then you have a fairly reliable & quick backup check for salinity. I had a glass floating hydrometer a while back which was actually very accurate (alas, I broke it), more so than any swingarm. Just need to compensate a bit for temperature if it's too far out of the floater's tested temp.

Photos that follow are of two swingarms & the floater that I had, showing the difference in readings with the same water. I believe my refractometer was reading just above 1.024, validating that the glass floater yielded the same reading, therefore accurate. I've since put marks on the swing arms at what should be the 1.025 mark when compared to the refractometer. So they're still useful as a backup instead of turfing them in the trash.

Coralife swingarm



IO Deep Six swingarm



Made in Taiwan floating glass hydrometer with built in thermometer



I actually still have a floating hydrometer, but it's for beer & wine making. Should still measure salinity though, since it has a specific gravity scale on it as well.

And almost forgot, I purchased an urchin at a LFS in Kelowna a month or so back & their water was way high in salinity on my refractometer.